Linux/Wireless

This page covers methods of connecting to wifi from Linux.

The methods break down as follows:

• Use /etc/network/interfaces
• Use wpa supplicant
• How to connect to encrypted vs. unencrypted wifi

Git Repos

As a note, there are some useful resources related to automatically joining wifi networks, mainly scripts developed for use with Raspberry Pis. These can be found here: https://git.charlesreid1.com/rpi/pi-join-wifi

Joining Wireless Networks

In Linux, joining a wifi network automatically, or from the command line, or otherwise without a visual desktop, is not a trivial task - even in 2017.

This page contains some notes on a few techniques for connecting to wifi networks, developed from experience with Raspberry Pis and other Linux computers with wireless devices built in (mostly laptops/virtual machines).

Using /etc/network/interfaces

Joining network with WPA encryption

NOTE: This method is working on Raspberry Pi platform as of April 2017.

Main Page: Linux/Wireless/2

To set the wireless network you want a Linux box to join, you can add the network name and passphrase to /etc/network/interfaces. Better yet, you can create one file for each network you want to have ready to go, and swap them in and out by sourcing them or not from the /etc/network/interfaces file.

First, put the wifi configuration information into a file. This will be called mynetwork.cfg, and will be stored in /etc/network/interfaces.d/mynetwork.cfg.

auto wlan0
allow-hotplug wlan0
iface wlan0 inet dhcp
    wpa-ssid NetName
    wpa-psk NetPassword

The next step is to reference this configuration file from the /etc/network/interfaces file. Here is what that file looks like:

source /etc/network/interfaces.d/mynetwork.cfg

The /etc/network/interfaces.d/ folder would contain credentials for several networks, and could be swapped out by editing /etc/network/interfaces.

Now you should try connecting to the network, and execute the command:

$ dhclient wlan0

Joining an open network

Repeat the above steps, but this time your wifi network's config file will look a little different for the open network:

auto wlan0
allow-hotplug wlan0
iface wlan0 inet dhcp
wpa-ssid LocalCoffeeShop

WPA Supplicant Method

NOTE: This is for WPA- and WPA2-encrypted networks only.

Main Page: Linux/Wireless/1

This method uses wpa_supplicant, and has been tested and works on a Rasbperry Pi.

The One Time Wham Bam Thank You Maam

Assuming your wireless device is wlan0,

$ wpa_supplicant -D nl80211,wext -i wlan0 -c <(wpa_passphrase "MyRouter" "MyPassword")

Set wireless network configuration

First add network configuration to /etc/wpa_supplicant/wpa_supplicant.conf

ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1

network={
    ssid="Your SSID Here"
    proto=RSN
    key_mgmt=WPA-PSK
    pairwise=CCMP TKIP
    group=CCMP TKIP
    psk="YourPresharedKeyHere"
}

Then edit /etc/network/interfaces and modify the wireless device to set the interface, and the wpa supplicant configuration file. Here is an example for a network with dynamic DHCP. This is the /etc/network/interfaces file:

# ------- DHCP ------------
iface wlan0 inet manual
wpa-roam /etc/wpa_supplicant/wpa_supplicant.conf
iface default inet dhcp

Reset network device

Bring network device down and back up:

ifdown wlan0
ifup wlan0

You should see the wireless network you specified in your wpa supplicant file when you run iwconfig:

iwconfig

You should also see an IP address when you run ifconfig:

ifconfig

To start wpa_supplicant manually:

# sudo /sbin/wpa_supplicant \
  -i wlan0 \
  -P /var/run/wpa_supplicant.wlan0.pid \
  -D nl80211,wext -c /etc/wpa_supplicant/wpa_supplicant.conf

Joining Wifi Networks On Boot

If you want to join wifi networks on boot, you can add a config file for the network you want to join, and put it in /etc/network/interfaces.d/

Then add the line to /etc/network/interfaces to source the above wifi network config file. Your system should know how to get an IP address from the router next time it needs one. Run:

$ dhclient wlan0

to flush and force dhcp to get a fresh IP address/connection.